The invention relates to a rotary drive device, having a device housing in which drive means are disposed which are in rotary driving connection with a power takeoff part supported rotatably relative to the device housing, the power takeoff part having a power takeoff disc which over at least a portion of its axial length is disposed in a bearing receptacle surrounded radially outward by the device housing, and the power takeoff disc being surrounded concentrically radially outward by at least one annular roller bearing unit which has a bearing assembly, the bearing assembly comprising the following: a plurality of rolling elements distributed over the circumference of the power takeoff disc; an annular inner running surface arrangement serving to radially brace the rolling elements relative to the power takeoff disc; and an annular outer running surface arrangement serving to radially brace the rolling elements with respect to the device housing.
A rotary drive device of this type, known from Patent Abstracts of Japan for JP 2007/127160 A, includes two racks, movable in alternation back and forth, in a device housing that cooperate as drive means with a power takeoff part in order to put the power takeoff part into reciprocating rotation. The power takeoff part has a power takeoff shaft, which meshes with the racks, and a power takeoff disc, formed integrally on the face end thereof and serving to as a force pickup. For rotary support, there is a roller bearing unit, concentrically surrounding the power takeoff disc, which roller bearing unit brings about bracing relative to the device housing. The roller bearing unit includes a bearing assembly, comprising an annular inner running surface arrangement, formed integrally onto the outer circumference of the power takeoff disc; an annular outer running surface arrangement, embodied on an additional bearing ring; and a plurality of rolling elements, which are braced on the two running surface arrangements. The bearing ring is inserted into an axially open bearing receptacle of the device housing, but it protrudes to some distance out of this bearing receptacle, as does the bearing assembly.
From WO 2008/075481 A1 and from Patent Abstracts of Japan for Japanese Patent JP 2008/157289 A forming the priority basis therefor, a rotary drive device of similar construction is known, but in which the power takeoff disc is embodied in multiple parts, resulting in a subdivision into a flange portion, embodied integrally with the power takeoff shaft, and a bearing portion joined to this flange portion in a manner fixed against relative rotation. For rotary support of the power takeoff part, rolling elements are used, disposed between the bearing portion and a bearing ring disposed concentrically to it and secured to the device housing.
DE 195 11 488 C2 describes a rotary drive device, called a pivoting piston motor, whose power takeoff part is embodied in shaftlike form and can be set into rotation by a pivoting piston that can be acted upon by fluid. A power takeoff disc on which components of relatively large dimensions can be fixed is not present in this rotary drive device.
Finally, DE 10 2006 015 478 A1 describes special embodiments of a roller bearing unit in which the running surface arrangements, cooperating with the rolling elements, are embodied on relatively thin wirelike bearing rings.
The two rotary drive devices discussed first above do make it possible, on their power takeoff disc which has a relatively large diameter, to fix components of relatively large dimensions and drive them to a rotary motion. However, the problem exists of overloading the roller bearing units used for rotary support, if the components to be driven have a high weight or for other reasons act with strong forces on the power takeoff part. Above all, forces that engage at a relatively great spacing from the longitudinal axis of the power takeoff part can result in unwanted wear, because of the resultant tilting moments.